Summary and Comment
ZTF photometry clearly exhibits many systematic effects
that are caused by a variety of different sources.
We have used millions of ZTF objects matched to
PS1 to derive corrections for these systematics.
These effects include the magnitude bias, the residual
spatial structure of the photometry, and residual field
offsets.
The additional ZTF photometric systematics that increase the
scatter measured between individual photometry points are
yet to be addressed. These are largely dependent on how
the photometry software responds to varying observing
conditions. In particular, the sky level, the seeing and
airmass. The problems (observation condition dependent systematics)
are most evident in fields with < 3000 calibrator stars.
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